Variable compression ratio internal combustion engine



1933- I I K. TSUNEDA 2,125,407

VARIABLE COMPRESSI ON RATIO INTERNAL COMBUSTION ENGINE Filed Sept. 1, 1936 EQQWAQ Patented. Aug. 2, 1938 UNITED STATES PATENT, OFFICE Kenjiro Tsuneda, Kyoto, Japan Application September 1, 1936, Serial No. 98,965 In Japan November 18, 1935 3 Claims. (01. 123-48) This invention relates to an internal combustion engine which is provided with means for varying the compression ratio for obtaining high thermal efliciency under varying conditions.

in internal combustion engines of the Otto cycle type, the compression ratio is limited within a safety range so as to prevent advanced ignition or detonation even when operating un- V der over load, or when operating with the richest mixture and at a considerably heated condition.

Therefore, it is not'possible under full load to obtain aflowable maximum compression ratio. Under a lighter load, it is desirable that a higher compression ratio be obtained, in view of the decrease of the amount oi suction or dilution of the mixture. However, in an old engine with a fixed volume of combustion chamber, it has been unavoidable that under lighter load the compression ratio greatly decreases below the maximum compression ratio allowed by the mixture then drawn in, whereby the thermal efllciency of the engine-isponsiderably lowered. An object of the invention is to provide the internal combustion engine with means by which 25. the-compression ratio can be conveniently varied according to the load of the engine, number of revolutions, nature of the fuel, etc.,'so as to, always obtain maximum thermal eiliciency under varying conditions.

With the above-mentioned object in view, ac-

cording to this invention, a movable member is incorporated in the wall of the combustion chamber, which movable member is adapted to be actuated by a mechanical means and moved from Y or toward the working piston, whereby the compression ratio can be readily'varied, so as to always obtain maximum compression ratio under varyin conditions. By such means, it is possibie to obtain increased thermal eiiiciency under varymg loads, and especiallyadvantageous results can be obtained when operating under lighter load. According to this invention, the means for varying the compremion ratio may be arranged on 46 the cylinder head, quite independently of the main part of the engine, so that the operation of the main parts is by no means affected. Any existingengine may be equipped with the compression ratio varying vmechanism according to 50 this invention, by a simple operation, without necessitating any substantial change in the construction of the main parts of the engine.

The invention will now be fully described with reference to the embodiment shown in the ac-' I6 companying drawing, in which:

Figure 1 is a longitudinal section of a portion of an internal combustion engine according to this invention; and

Figure 2 is. a planthereof partly in section.

Referring to the drawing, the reference numeral 5 l designates a'cylinder, 2 a cylinder head, and 3 the main piston. The cylinder head 2 is provided with a cavity 4 opposite to the piston 3, and in this cavity 4 there is slidably mounted a pistonlike movable member 5. Said movable member 5 10 has a central rod I extendingupwardly and formed with a screw-thread 6. Between the upper wall 8 of the cavity 4 and a top plate 9 there 'is arranged a pinion l0 having its axial .bore internally screw-threaded and engaging with said 15 threaded rod 1. Engaged with said pinion I0 is a toothedrack II, which is adapted to be moved horizontally on the cylinder head.

The toothed rack ll may be actuated by any manually or automatically controlled means. For 20 automatic control, means may be provided which is responsive to variation of pressure or temperature of explosion gas, or suction pressure in the inlet manifold, according to variations of the load of the engine and other varying conditions. 5 in the embodiment shown, means responsive to variation of explosion gas pressure is provided for actuating the rack ii. A pipe l6 which is-in communication with the combustion chamber of the engine, is connected to the inlet side of the 30 valve chest containing a double-seated valve l2. Said valve l2 acts as an inlet and outlet controlling valve, and is opened by the ingress of the explosion gas, the latter being introduced into a servo-motor cylinder l3, acts upon a servo-motor 5 piston M. A rod l5 oi said piston i4, is connected to the toothed rack II.

when the pinion no is rotated in either direction by the toothed rack ll, the threaded rod 1 is raised or lowered, and the position of the movable 4,0

' .member 5 is varied accordingly. Thus, the efl'ective volume of the combustion chamber is varied for the purpose of obtainingthe desired compression ratio. When the automatic controlling mechanism as mentioned above with reference to Figure 2 is employed, according to-the reduction of the load and consequently according to the decrease of the maximum explosiongas pressure, the valve I2 is maintained in closed-position by the action of a spring I1, and the gas in the servomotor cylinder is discharged through a discharge pipe 19 by the action of a spring [8 acting upon the piston ll. Together with the piston rod 15, the toothed rod II is moved in such a direction that the movable member 5 is lowered, thereby automatically increasing the compression ratio. Upon increase of the load, increased explosion gas pressure will open the inlet side of the valve i2, closing the outlet side thereof at the same time,

',and increasing the pressure within the servomotor cylinder, whereby the rack H and the associated mechanism are actuated in the reverse direction, so that the'mevable member 5 is lifted. Thus, the compression ratio is automatically decreased. 1

During the operation of the engine, the movable member 5 is subjected to high temperature, and due to the fact that it is moved intermittently and irregularly for a short stroke, it is liable to be subjected to undue expansion causing a tight fit in the cavity 4, which will prevent the'easy movement of the member 5 for varying the compression ratio. In order to remove such a disadvantage, the movable member 5 is preferably made hollow, and the rod I provided with a canal 20 within which is a water tube 2|, which has an outer diameter smaller than the inner diameter of the canal 20, thus leaving an annular passage aroundthe tube 2|. The lower end of the water tube 2|, is in communication with the holl w chamber within the member 5, and at the upper end it is connected to a water feed pipe 22. A water pipe 23 is connected to the canal 20. By such means cooling water is continuously fed into the movable member 5, for cooling the same.

being heated to a high temperature.

In the drawing a packing 24, is fitted at the sliding portion of the movable member 5, and a piston ring 25, is fitted tosaid piston-like movable member. 26 is a bearing. 21 is a key for guiding the movement of the rod 1. 28 is a spring for preventing vibrating movement of the member 5.

What I claim is:

l. A variable compression ratio internal coinbustion engine comprising a cylinder, a main piston in said cylinder, a cylinder head having a cavity and forming a combustion chamber to-' gether with said cylinder and the'main piston, a piston-like movable member slidably mounted in said cavity in the cyiinder head, a threaded cen- V tral rod fixed to said piston-like movable member, a'pinion having its bore internally screw-threaded and engaging with said threaded central rod, a toothed rack engaging with said pinion and adapted to be moved horizontally on the cylinder head, a servo motor cylinder, a servo-motor piston This will also 1 prevent the lubricant from splitting up, due to in said servo-motor cylinder and connected to said toothed rack, a pipe connecting said servo-motor cylinder to said combustion chamber, a controlling valve in said pipe for controlling the flow ofexplosion gas from said combustion chamber into said servo-motor cylinder.

2. A variable compression ratio internal combustion engine comprising a cylinder, a main piston in said cylinder, 8. cylinder head having a cavity and forming a combustion chamber together with said cylinder and the main piston, a piston-like movable member slidably mounted in said cavity in the cylinder head, a threaded central rod fixed to said piston-like movable member, a pinion having its bore internally screw-threaded and engaging with said threaded central rod, 9. toothed raci: engaging with said pinion and adapted to be moved horizontally on the cylinder head, a servo-motor cylinder, a servo-motor piston in said servo-motor cylinder and connected to said toothed rack, a pipe. connecting said servomotor cylinder to said combustion chamber, a double-seated valve acting m an inlet and outlet controlling valve and controlling on one hand the flow of explosion gas from said combustion cham her to said servo-motor cylinder, and on the other hand controlling the flow of gas from said servomotor cylinder.

3. A variable compression ratio internal combustion engine comprising a cylinder, a main piston in said cylinder, a. cylinder head having a' cavity and forming a combustion chamber together with said cylinder and the main piston, a

hollow piston-like movable member slidably mounted in said cavity in the. cylinder head, a

threaded central hollow rod fixed to said pistonlike movabie member and having its bore formed as a water canal which is in communication with a hollow chamber in said piston-like movable member, a pinion having its bore internally screw threaded and engaging with said threaded central rod, a toothed rack engaging with said pinion and adapted to be moved horizontally on the cylinder head, a servo-motor cylinder, a servo-motor piston in said servo-motor cylinder and connected to said toothed rack, a pipe connecting said servomotor cylinder to said combustion chamber, a controlling valve in'said pipe for controlling the how of explosion gas from said combustion chamber into the said servo-motor cylinder.

KnNJmo TSUNEDA. 

